Amazon.com : API NITRATE 90-Test Freshwater and Saltwater Aquarium Water Test Kit for $2.86

[nbaiju]

if you clip the coupon on the product page.

https://www.amazon.com/API-Nitrate-Freshwater-Saltwater-Aquarium/dp/B002DVVICS/ref=sr_1_5?dchild=1&keywords=api+nitrate+test+kit&qid=1607553509&sr=8-5